INDUCTIVELY COUPLED PLASMA APPARATUS WITH NOVEL FARADAY SHIELD
An antenna assembly, comprising: an antenna; a dielectric enclosure surrounding the antenna; and a Faraday shield, disposed around the antenna, and arranged between the antenna and the dielectric enclosure, wherein the Faraday shield comprises a non-uniform opacity along an antenna axis of the antenna, wherein a first opacity of the Faraday shield at a first position along the antenna axis is greater than a second opacity of the Faraday shield at a second position along the antenna axis of the antenna.
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The disclosure relates generally to processing apparatus, and more particularly to plasma based ion sources.
BACKGROUND OF THE DISCLOSUREIn the present day, plasmas are used to process substrates, such as electronic devices, for applications such as substrate etching, layer deposition, ion implantation, and other processes. Some processing apparatus employ a plasma chamber that generates a plasma to act as an ion source for substrate processing. An ion beam may be extracted through an extraction assembly and directed to a substrate in an adjacent chamber. This plasma may be generated in various ways.
In various commercial systems, an antenna is disposed outside the plasma chamber, proximate to a dielectric window. The antenna is then excited using an RF power supply. The electromagnetic energy generated by the antenna then passes through the dielectric window to excite feed gas disposed within the plasma chamber by inductive coupling. This configuration provides a relatively simple construction, and may generate dense plasmas suitable for generating a high current ion beam using extraction through an extraction aperture that may be placed centrally within the plasma chamber. However, such inductively coupled plasmas (ICP) may tend to have a peaked plasma density in the middle of the chamber, and may not be ideal for long apertures or for multi-aperture high current ion beam systems, where two or more apertures are arranged as parallel slots along one edge of the plasma chamber.
Another approach may to provide an ICP antenna within a plasma source to excite the gas in the surrounding chamber. In such case, the antenna will be protected by a material that acts as an rf window, where the rf window material may be shaped into an enclosure that surrounds the antenna. However, such windows may be susceptible to degradation during plasma source operation. An ideal ICP system should have just inductive coupling to power the plasma. However, an RF antenna also couples capacitively with the plasma in practical implementations. A small capacitive coupling from antenna to plasma is desired because plasma is ignited capacitively. However, too much capacitive coupling is detrimental to the plasma source because a relatively higher degree of capacitive coupling from the antenna to plasma will decrease plasma density and increase the electron temperature of the plasma. This fact may lead to an increase of plasma potential in the plasma and consequently an increase of ion energy of ions crossing the plasma sheath (the thin layer separating the plasma from the wall) and impinging on surfaces such as an RF window or other shield, resulting in unwanted sputtering of material from the chamber walls and the antenna in the case antenna is immersed in the plasma. In turn, the unwanted sputtering may degrade RF window lifetime and generate particles within the plasma source.
With respect to these and other considerations the present disclosure is provided.
BRIEF SUMMARYIn one embodiment, an antenna assembly may include an antenna, a dielectric enclosure, surrounding the antenna, and a Faraday shield, disposed around the antenna, and arranged between the antenna and the dielectric enclosure. The Faraday shield may include a non-uniform opacity structure, wherein an opacity of the Faraday shield changes between a first region of the antenna and a second region of the antenna.
In another embodiment, an ion source is provided. The ion source may include a plasma chamber, an extraction plate, disposed on a side of the source chamber, and an antenna assembly, disposed within the plasma chamber. The antenna assembly may include a linear antenna, having a grounded end, and a powered end, the linear antenna extending along an antenna axis. The antenna assembly may also include a dielectric enclosure, surrounding the linear antenna, the dielectric enclosure being elongated along the antenna axis. The antenna assembly may further include a Faraday shield, disposed around the linear antenna, and arranged between the linear antenna and the dielectric enclosure, wherein the Faraday shield comprises a non-uniform opacity structure, wherein an opacity of the Faraday shield changes along the antenna axis.
In an additional embodiment, a processing apparatus is provided. The processing apparatus may include a plasma chamber, an extraction plate, disposed on a side of the source chamber, and a processing chamber, having a substrate holder, disposed opposite the extraction plate, and an antenna assembly, disposed within the plasma chamber. The antenna assembly may include a linear antenna, having a grounded end, and a powered end, the linear antenna extending along an antenna axis. The antenna assembly may also include a dielectric enclosure, surrounding the linear antenna, where the dielectric enclosure is elongated along the antenna axis. The antenna assembly may further include a Faraday shield, disposed around the linear antenna, and arranged between the linear antenna and the dielectric enclosure, wherein the Faraday shield comprises a non-uniform opacity structure, wherein an opacity of the Faraday shield changes along the antenna axis.
The drawings are not necessarily to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict exemplary embodiments of the disclosure, and therefore are not be considered as limiting in scope. In the drawings, like numbering represents like elements.
DETAILED DESCRIPTIONAn apparatus, system and method in accordance with the present disclosure will now be described more fully hereinafter with reference to the accompanying drawings, where embodiments of the system and method are shown. The system and method may be embodied in many different forms and are not be construed as being limited to the embodiments set forth herein. Instead, these embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the system and method to those skilled in the art.
Terms such as “top,” “bottom,” “upper,” “lower,” “vertical,” “horizontal,” “lateral,” and “longitudinal” may be used herein to describe the relative placement and orientation of these components and their constituent parts, with respect to the geometry and orientation of a component of a semiconductor manufacturing device as appearing in the figures. The terminology may include the words specifically mentioned, derivatives thereof, and words of similar import.
As used herein, an element or operation recited in the singular and proceeded with the word “a” or “an” are understood as potentially including plural elements or operations as well. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as precluding the existence of additional embodiments also incorporating the recited features.
Provided herein are apparatus for improved ICP plasma sources that are driven by an internal antenna. In particular, a Faraday shield configuration is disclosed that is applicable to a linear rf antenna. As detailed below, a novel Faraday shield design is provided that exhibits a non-uniform opacity along the antenna length of a linear antenna. While this disclosure will focus on embodiments of a linear antenna, the present embodiments will cover a non-uniform opacity Faraday shield as applied to other antenna geometries and configurations.
Turning to the figures,
The linear antenna 12 may be a single conductive structure, such as a metallic structure that loops back upon itself as discussed below with respect to
In some embodiments, the linear antenna 12 may be a hollow tube that may be cooled by a cooling fluid provided within the hollow tube, such as a DI (de-ionized) water, ethylene glycol, silicone oil, nano-ester fluids etc. In addition, in some embodiments, a cooling gas may be provided in the enclosure formed by the dielectric enclosure 16, which cooling gas may surround the linear antenna and act as a coolant during operation.
In some embodiments, the Faraday shield 14 may be affixed to an inner wall of the dielectric enclosure 16, such as a patterned copper foil that is glued or cemented to the dielectric enclosure 16. In other embodiments, the Faraday shield 14 may be a separate conductive structure that is not adhered to the dielectric enclosure. The Faraday shield may be formed of a plurality of ribs, circumferentially surrounding the linear antenna.
Turning to
In some non-limiting embodiments, the plasma chamber 102 may be elongated along the X-axis, such that an extraction aperture 109 together with the linear antenna assembly 10 is also elongated along the X-axis. In particular embodiments, the linear antenna assembly 10 and extraction aperture 109 may be elongated to generate an elongated ‘ribbon’ ion beam when a plasma is formed in the plasma chamber 102, having a width up to 400 mm along the X-axis, with a height from several millimeters to several centimeters.
In operation, the role of the cylinder formed by the dielectric enclosure 16 is to allow transmission of the RF power from the linear antenna 12 to a rarefied gas that is provided inside the plasma chamber, but external to the dielectric enclosure 16. In particular, the dielectric enclosure 16 serves as a sealing wall to house the linear antenna 12 and define an internal chamber that separates and seals the internal chamber from the rest of the plasma chamber 102. In this manner, a separate ambient may be provided inside the cylindrical region defined be the dielectric enclosure 16, with respect to the ambient of the plasma chamber surrounding the dielectric enclosure 16.
As further depicted in
Turning now the
The Faraday shield 14A includes a plurality of ribs 112 that are arranged as a non-uniform opacity structure, wherein an opacity of the Faraday shield 14 changes along the antenna axis, meaning along the X-axis. A function of the non-uniform opacity of the Faraday shield 14A is to change capacitive coupling as a function of position along the X-axis between the linear antenna 12 and a plasma formed within the plasma chamber 102. By varying the capacitive coupling of linear antenna 12 and a plasma the resultant electron temperature and ion density may be varied along this direction.
To further explain this phenomenon,
A bottom region of the figures illustrates a plasma region 304 that is separated from the dielectric enclosure 16 by a thin plasma sheath, shown as plasma sheath 302. In
In sum, the comparison of
Returning to
To illustrate this point further,
If a capacitor is inserted in the grounded leg of linear antenna 12, and this terminal capacitor has such capacitance value
which result comes from the condition that capacitive reactance is equal to half the inductive reactance of the linear antenna 12, then the situation as depicted in
Thus, for example, in the embodiment of
Erz=√{square root over (Er2+Ez2)} (3)
which field is proportional to the voltage on the linear antenna 12. For this reason, providing a Faraday shield 14 around the linear antenna 12, where the Faraday shield 14 has uniform opacity or transmission along the X-axis, will not be appropriate because this configuration will give rise to zones of monotonically varying electrostatic coupling and consequently non-uniform plasma density along the linear antenna 12. Said differently, and referring again to
In contrast, the Faraday shield 14A of
In one embodiment, providing a Faraday shield with a non-uniform opacity, such as a linearly decreasing opacity from the left side (where opposing ends of linear antenna 12 are located) to the right side (U-shaped portion of linear antenna, furthest right) will generally compensate for the deceased voltage along the linear antenna from left to right. However, the present inventors have discovered that a Faraday shield having a non-linear variation in opacity as a function of position along the X-axis may provide a more uniform electrostatic coupling along the X-axis. In particular, using high frequency simulation software (HFSS) modelling that a Faraday shield having a transmission obeying a Hill function along the linear antenna length will generate uniform electrostatic coupling and consequently uniform plasma density along the linear antenna.
To illustrate the advantage of a non-uniform opacity Faraday shield,
In additional embodiments, a non-uniform opacity Faraday shield where opacity varies along an antenna axis may be used in conjunction with other antenna designs, different than a linear antenna.
In view of the above, the present disclosure provides at least the following advantages. As a first advantage, the erosion of an rf window used with an ICP antenna may be reduced using the new non-uniform opacity Faraday shield configuration. In addition, a more uniform plasma density and consequently uniform extracted ribbon ion beam current density may be achieved in an ion source arranged according to the present embodiments.
While certain embodiments of the disclosure have been described herein, the disclosure is not limited thereto, as the disclosure is as broad in scope as the art will allow and the specification may be read likewise. Therefore, the above description are not to be construed as limiting. Thus, a non-uniform opacity Faraday shield of adequate shape and topology may be used in conjunction with solenoidal antenna, flat spiral antenna, helical antenna, or circular antenna to mitigate the detrimental effect of non-uniform voltage distribution along their length. Those skilled in the art will envision such modifications within the scope and spirit of the claims appended hereto.
Claims
1. An antenna assembly, comprising:
- an antenna;
- a dielectric enclosure, surrounding the antenna; and
- a Faraday shield, disposed around the antenna, and arranged between the antenna and the dielectric enclosure, wherein the Faraday shield comprises a non-uniform opacity along an antenna axis of the antenna, wherein a first opacity of the Faraday shield at a first position along the antenna axis is greater than a second opacity of the Faraday shield at a second position along the antenna axis of the antenna.
2. The antenna assembly of claim 1, the Faraday shield being affixed to an inner wall of the dielectric enclosure.
3. The antenna assembly of claim 1, wherein the Faraday shield comprises a plurality of ribs, circumferentially surrounding the antenna.
4. The antenna assembly of claim 1,
- wherein the antenna comprises a linear antenna, having a grounded end, and a powered end, the linear antenna extending along the antenna axis;
- wherein the dielectric enclosure is elongated along the antenna axis.
5. The antenna assembly of claim 4, wherein the Faraday shield further comprises a plurality of ribs and a spine, the spine extending parallel to the antenna axis and arranged to connect the plurality of ribs to one another.
6. The antenna assembly of claim 4, wherein the linear antenna comprises a hairpin structure, the hairpin structure comprising a first linear portion that extends from the powered end, a second linear portion that extends from the grounded end, and a connecting portion, connecting the first linear portion to the second linear portion,
- wherein the grounded end is disposed next to the powered end, wherein a side of the linear antenna where the grounded end and powered end are disposed comprises a higher voltage side of the linear antenna, and wherein a side of the linear antenna where the connecting portion is located comprises a lower voltage region of the linear antenna.
7. The antenna assembly of claim 6, wherein Faraday shield exhibits the first opacity at a first end of the Faraday shield, surrounding the powered end of the linear antenna, and exhibits the second opacity at a second end of the Faraday shield, surrounding the connecting portion of the linear antenna.
8. The antenna assembly of claim 7, wherein the non-uniform opacity varies along the antenna axis according to a Hill function.
9. A processing system, comprising:
- a plasma chamber; and
- an antenna assembly, disposed within the plasma chamber, the antenna assembly comprising: a linear antenna, having a grounded end, and a powered end, the linear antenna extending along an antenna axis; a dielectric enclosure, surrounding the linear antenna, the dielectric enclosure being elongated along the antenna axis; and a Faraday shield, disposed around the linear antenna, and arranged between the linear antenna and the dielectric enclosure, wherein the Faraday shield comprises a non-uniform opacity along the antenna axis of the antenna, wherein a first opacity of the Faraday shield at a first location along the antenna axis is greater than a second opacity of the Faraday shield at a second location along the antenna axis.
10. The processing system of claim 9, the Faraday shield being affixed to an inner wall of the dielectric enclosure.
11. The processing system of claim 9, wherein the Faraday shield comprises a plurality of ribs, circumferentially surrounding the linear antenna.
12. The processing system of claim 11, wherein the Faraday shield further comprises a spine, the spine extending parallel to the antenna axis and arranged to connect the plurality of ribs to one another.
13. The processing system of claim 9, wherein the linear antenna comprises a hairpin structure, the hairpin structure comprising a first linear portion that extends from the powered end, a second linear portion that extends from the grounded end, and a connecting portion, connecting the first linear portion to the second linear portion,
- wherein the grounded end is disposed next to the powered end, wherein a side of the linear antenna where the grounded end and powered end are disposed comprises a higher voltage side of the linear antenna, and wherein a side of the linear antenna where the connecting portion is located comprises a lower voltage region of the linear antenna.
14. The processing system of claim 13, wherein Faraday shield exhibits the first opacity at a first end of the Faraday shield, surrounding the powered end of the linear antenna, and exhibits the second opacity at a second end of the Faraday shield, surrounding the connecting portion of the linear antenna.
15. The processing system of claim 14, wherein the non-uniform opacity varies along the antenna axis according to a Hill function.
16. A processing system, comprising:
- a plasma chamber;
- an extraction plate, disposed on a side of the plasma chamber;
- a processing chamber, having a substrate holder, disposed opposite the extraction plate; and
- an antenna assembly, disposed within the plasma chamber, the antenna assembly, comprising: a linear antenna, having a grounded end, and a powered end, the linear antenna extending along an antenna axis; a dielectric enclosure, surrounding the linear antenna, the dielectric enclosure being elongated along the antenna axis; and a Faraday shield, disposed around the linear antenna, and arranged between the linear antenna and the dielectric enclosure, wherein the Faraday shield comprises a non-uniform opacity structure, wherein an opacity of the Faraday shield changes along the antenna axis.
17. The processing system of claim 16, wherein the Faraday shield comprises a plurality of ribs, circumferentially surrounding the linear antenna; and
- a spine, the spine extending parallel to the antenna axis and arranged to connect the plurality of ribs to one another.
18. The processing system of claim 16, wherein the linear antenna comprises a hairpin structure, the hairpin structure comprising a first linear portion that extends from the powered end, a second linear portion that extends from the grounded end, and a connecting portion, connecting the first linear portion to the second linear portion,
- wherein the grounded end is disposed next to the powered end,
- wherein a side of the linear antenna where the grounded end and powered end are disposed comprises a higher voltage side of the linear antenna, and wherein a side of the linear antenna where the connecting portion is located comprises a lower voltage region of the linear antenna.
19. The processing system of claim 18, wherein the Faraday shield exhibits a first opacity at a first end of the Faraday shield, surrounding the powered end of the linear antenna, and exhibits a second opacity, less that the first opacity, at a second end of the Faraday shield, surrounding the connecting portion of the linear antenna.
20. The processing system of claim 19, wherein the opacity varies along the antenna axis according to a Hill function.
Type: Application
Filed: Oct 12, 2022
Publication Date: Apr 18, 2024
Applicant: Applied Materials, Inc. (Santa Clara, CA)
Inventors: Costel Biloiu (Rockport, MA), Adam Calkins (Newmarket, NH), Benjamin Alexandrovich (Brookline, MA), Solomon Belangedi Basame (Middleton, MA), Kevin M. Daniels (Lynnfield, MA)
Application Number: 17/964,621